Un sonar latéral de nouvelle génération

Abstract
Sidescan images of the sea-floor usually suffer from artefacts caused by the attitude variations of the towed platform. In collaboration with IFREMER, we are designing a system that compensates for yaw, pitch and roll in real time, i.e. during the whole ping cycle. The 4 m long antenna is made of 3 arrays working at 110 kHz. It enables ranges up to 1000 m and the angular resolution is 0.25° i.e. 1 m scan resolution for a 250 m range. The transmit array is made of 36 elements with 80 mm spacing. There are two identical receiving arrays, containing 32 active pieces each, with 120 mm spacing. The duplication of the receiving channel will give a bathymetric capability. Data provided by an attitude station are used to control the numerical beam-steering performed at transmit and during receive. On the other hand, 16 focal zones have been set to achieve a constant along-track resolution of 1 m up to 250 m range. In addition, focusing reduces the side-lobes level. The experimental results in water tank are in good agreement with the numerical model. First data and images were gathered during a campaign at sea in November 93.